<!DOCTYPE html>
<html>

	<head>
		<meta charset="UTF-8">
		<title></title>
	</head>

	<body>
		<script type="text/javascript">
			class Animal {
				constructor() {
					this.foots=4;
				}
			}
			
			//继承于
			class Dog extends Animal{
				constructor(){
					//把Animal先实例化
					super();
					
				}
			}
			
			let d=new Dog();
			console.log(d);
			
			//实例化
			class blueCat extends cat{
				constructor(){
					//把Animal先实例化
					super();
					
				}
			}
			
		</script>
	</body>

</html>